1. Technical Field
The invention concerns digital video recorder, and more particularly a method and apparatus for removing commercial interruptions from video programming.
2. Description of the Related Art
Various devices have been developed to enable consumers to record video and/or audio programs for later presentation. Such devices include tape recorders, videocassette recorders, recordable compact discs, and most recently, recordable digital video discs (DVD). Hard drives and magneto optical discs have also been used.
One feature that is desirable for an MPEG media recorder is the ability to automatically identify and selectively skip segments of a recorded video signal. For example, such a feature may be useful for automatically editing out commercial messages from recorded television broadcast signals. Commercial skip is an important feature in the field of videocassette recorders. In this regard, various systems have been disclosed in the context of video cassette recorders to address this problem.
Conventional commercial skip technology in VCRs has used fading to dark frames as a cue for identifying and deleting commercial advertisements. These dark or black frames are used to generate a map of possible commercials in recorded television programming. However, this conventional approach is not entirely satisfactory because it requires one to wait while the system returns to the beginning of the segment to mark the commercial, and it uses tape sync pulse encoding of events/Startskip/StopSkip. Moreover, because conventional VCRs do not use MPEG type encoding, they cannot take advantage of more sophisticated video processing methods that can be applied for detecting video program transitions such as may occur during commercial advertisements.
In recent years, more advanced systems that record video programs to a hard disk have also implemented commercial skip features. Such systems use a specific set of rules for identifying commercials and commercial groups. In general, commercials are separated from each other and from programs by video fades to black, and audio fades to silence. Accordingly, commercials can be identified by the occurrence of certain events that are simultaneous black video and no audio. A commercial skipping device can be configured to determine when a video signal is sufficiently black and the audio is at a sufficiently low level so as to determine the occurrence of an event.
Commercial groups are groups of individual commercials that are to be skipped. The various rules for determining commercial groups are rules specifying commercial lengths, and number of commercials together. For example, if there were five events detected, with exactly one minute between them, it can fairly be assumed that these collectively represented a commercial group. The goal is to skip commercial groups. Thus, for example, the device can use “A” marks at the beginning of the commercial group (to tell the device to start skipping), and “B” marks at the end of the commercial group (to tell the device to stop skipping and resume normal video and audio output). However, these systems continue to use techniques based on principals of analog tape recording, and the skip information is a simple manipulation of the control track pulse width.